Jitter measurement of the multi-level PAM eye diagram

Abstract

A method for measuring litter in multi-level Pulse Amplitude Modulation (PAMn) eye diagrams, employing one-way analysis of variance (ANOVA) and image processing techniques. The procedure begins by importing a photo or digital file of a PAMn eye diagram and editing it to form a one Unit Interval (1UI) PAMn pattern. It proceeds by acquiring vertical histograms along the amplitude axis for both the horizontal lane (hlane) at the middle of a level and mixed lanes at one end of the PAMn pattern. Gaussian fits are then applied to these histograms to ascertain jitter characteristics. The key fitting parameters, including the hlane mean, the level mean, and their mean shift, are used to determine Deterministic Jitter (DJ), while the widths of the hlane and level contribute to the assessment of Random Jitter (RJ). This method provides a detailed and advanced evaluation of litter characteristics essential for high-speed serial communication systems.

The invention claimed is: 
     
       1. A method comprising the steps for:
 importing a photo or a digital file of a multi-level Pulse Amplitude Modulation (PAMn) eye diagram captured from a digital sampling oscilloscope; 
 editing the PAMn eye diagram from a configuration with 2UI (unit interval) or multiple UI to a 1UI PAMn pattern using a specifically defined image processing algorithm; 
 reconfiguring the pixel size and scale of the 1UI PAMn pattern for jitter measurement; 
 performing jitter measurements to determine jitter testing parameters, including the level mean and level mean shift associated with Deterministic Jitter (DJ), and a level width (standard deviation) corresponding to Random Jitter (RJ), for a level histogram within the 1UI PAMn pattern; 
 reporting the jitter parameters, including the level mean and level mean shift, the level width, and their contribution to Total Jitter (TJ), for the PAMn level histogram. 
 
     
     
       2. The method of  claim 1 , wherein the steps of editing the PAMn eye diagram to a 1UI PAMn pattern comprises:
 sampling two points, (x1, y1) and (x2, y2), on a horizontal line of the PAMn eye diagram, where both points exhibit the same local pattern and x1<x2; 
 sampling a third point (x3, y3) at the eye center in the PAMn eye diagram, where x1<x3<x2; 
 converting the color image of the PAMn eye diagram into a grayscale image using image processing techniques; 
 vertically cropping the eye diagram into two parts: the first part (img1) from x1 to x3, and the second part (img2) extending from x3 to x2; 
 recombining the two cropped images in reverse order, such that img3 is created by placing img2 before img1, forming the 1UI PAMn image. 
 
     
     
       3. The method of  claim 1 , wherein the step of performing jitter measurement to determine litter testing parameters for a level histogram comprises:
 selecting a sampling point for the horizontal lane (hlane) signal at the midpoint of the level within the 1UI PAMn pattern; 
 acquiring histogram for the hlane signal on the vertical axis at the selected sampling point; 
 fitting a Gaussian distribution to the hlane histogram to determine the hlane mean (μ 0 ) and hlane width (σ 0 ), where the width corresponds to the standard deviation of the distribution; 
 selecting a sampling point for the level signal near one end of the level; 
 acquiring a histogram of the level signal on the vertical axis at the selected sampling point; 
 fitting Gaussian distribution to the level histogram to determine its mean (μ) and width (σ), where the width also corresponds to the standard deviation of the distribution; 
 calculating the mean shift (Δ), defined as the difference between the mean of the level histogram (μ) and the mean of the hlane histogram (μ 0 ), to assess characteristics of deterministic jitter (DJ) of the level histogram.